Monday, March 2, 2009

Portrait: Great Horned Owl

Great Horned Owls begin strengthening their pair bonds in the middle of winter. As the breeding season approaches, which for this species is very early, the pair will often roost close together. This handsome couple is roosting together six weeks before breeding. The female is on the right (larger and, in this case, paler). This pair exhibits some of the typical range of colour variation found in Manitoba.


Of course, they are not always side-by-side.


And sometimes they engage in some interesting behaviour – here they seem to be kissing. The female is standing up and the male “lying” in the boughs.


Once they choose a nest site, they do not take long to start breeding. In Manitoba, suburban pairs will often lay in February, pairs in rural areas later. This mild winter of 2006 saw some exceptionally early nests in Manitoba with laying beginning in mid January. Egg laying in 2007 in Winnipeg did not begin until February (which is still early compared to long-term averages). In 2008, the earliest egg laying was 26th January but in the colder 2009 the first nest I found incubating was on February 19th. Incubating females sit very low on the nest as they must keep the eggs warm with their brood patch (when it is -30°C, they cannot leave the nest for more than a few minutes).


When the young hatch the females start to sit a little higher but still use their contour feathers to brood the chicks.


On warmer days they may sit very high


As the young start to get bigger, and can thermoregulate better, she may sit beside them. You can see the remains of food items in the nest.


The male roosts close to the nest and brings food for his family. As the chicks get bigger, the female will start to leave the nest for long enough to hunt. This female has caught an eastern cottontail in broad daylight (cottontails are plentiful in suburban Winnipeg).


Not rabbit again mum! Actually suburban owls have quite a diverse diet and they have not apparently made a dent in the cottontail population (as many gardeners constantly point out to me).


Most of the nesting efforts I have observed in our area have produced two chicks. Sometimes they have just one chick, but other times there are three.


In roughly 6 weeks, their plumage has gone from pure white to buffy and they are ready to leave the nest.


Sometimes they “branch”, i.e. leave the nest to perch in branches in the same tree above the nest. Some studies suggest that branching increases their likelihood of survival by reducing predation risk.


Out of the nest! This chick fledged on 31st March 2006 (earliest recorded fledging in Manitoba) and tried hard to maintain an air of humility when photographed on their first night out... or is that befuddlement?


Here are some more portraits of recently fledged youngsters. You'll notice how the flight feathers are the most fully developed and that the back is already quite developed (adult-like), unlike the fluffy down of the underparts, which is retained the longest.


From their first seemingly timid short hops out of the nest, they must quickly learn to fly. This often involves a lot of flapping to strengthen their muscles before they actually let go. Gradually, they gain confidence…


And a little encouragement always helps!


Flight brings many adventures but landing always seems the most difficult task to master. They even have to learn one of life's lessons that I struggle with, viz. to get upright again sometimes you have to let go first!


Soon, they become adept… even at landing


And can fly clear across large open areas, even across rivers.


By mid August they have all but completed their first prebasic moult and look like their parents. In the photo of the youngster stretching, notice the somewhat pointed shape and uniform wear of the remiges indicating a hatch year bird.


Siblings still hang out together, sometimes striking poetic poses...


Perched out like this, they may look their adults; however, they haven’t mastered hunting on their own yet and their parents still answer their raspy begging calls.


They are also good at getting up to mischief!


Not sure what they're up to but...


This youngster has decided to tear into a piece of bark and rip it off the branch – practice perhaps for dismembering prey.


And they still like to bug their parents. Mum (upper right) does not seem too impressed with her wee-un's antics.


...but, in the blink of an eye, they will strike out alone, off to terrorise the night sky... gracefully!


...and purposely!
You can see more of my owl photography at: http://artusophotos.com/3_Nightbirds/index.htm

3 comments:

  1. That was a most interesting post.Your owl pictures are great.
    Blessings,Ruth

    ReplyDelete

 
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